Effect Of Solute Content Research Articles

Effects of solute content on microstructure of nano precipitate-fine grain synergistically reinforced copper alloys

ABSTRACT Alloying of Fe, Co was reported to tailor microstructure of copper alloys into a nanoprecipitate-fine grain (NPFG) structure, i.e. nano-sized iron-rich precipitates dispersed inside refined grains. Here, we investigate the solute effect of Sn, Zn on NPFG structure in as-cast copper samples. Mechanisms are proposed to account for the solute effect on precipitate and grain features. Solutes restrict coarsening but facilitate undesirable morphology transition from spherical to angular of iron-rich precipitates. Meantime, solutes allow more precipitates to be active in the nucleation of copper and consequently induce finer grains. Minor Sn is added to optimise NPFG structure and leads to an excellent strength–ductility combination in Cu–1.5Fe–0.1Sn (wt-%) alloy. This work provides a solute-alloying strategy to achieve desired mechanical properties in metals.

Novel cost-effective Fe-based high entropy alloys with balanced strength and ductility

Based on the current pseudo-binary design strategy of eutectic high entropy alloy (EHEA), a novel approach to design eutectic or near-eutectic HEA was proposed. The eutectic composition can be experimentally specified through adjusting the atomic content ratio (RI/F) of the intermetallic forming elements to the face-centered cubic (FCC) forming elements in an equiatomic HEA system. This adjustment was done by reducing the contents of intermetallic forming elements (Mo and Cr) and accordingly increasing the content of FCC forming element (Fe). Based on this new design strategy, a cost-effective Fe-based near EHEA (Fe45Ni25Cr5Mo25 alloys) were designed and produced after decreasing the RI/F value from 1 to 3/7. The as-cast alloy was associated with compressive strength of 1661 MPa and ductility of 17%. It was considered that the hard trigonal μ phase together with the relatively ductile lamellar eutectic structure were responsible for the high combined properties. In addition, the effects of solute content, Mo and Cr in particular, on the microstructure and mechanical properties of this type of HEAs were also studied.

Correlation between dislocation organization and slip bands: TEM and AFM investigations in hydrogen-containing nickel and nickel–chromium

Various forms of the plastic deformation in single crystals are studied in pure and hydrogen-containing nickel and nickel alloys oriented for single slip [135] and strained in the stage III regime (shear strain, γ=0.8). The heterogeneity of deformation is investigated at two distinct scales: slip bands and dislocation structures, using atomic force microscopy (AFM) and transmission electronic microscopy (TEM). Size and distribution of slip band thicknesses and geometrically necessary boundary (GNB) spacing are comparable. GNB structures both screen the long-range stress fields and decrease the mean free path of mobile dislocations, whereas equiaxed cells only impede dislocation motion through their role as obstacles. Consequently, GNB formation localizes deformation in specific slip bands. Additionally, the observed similarity between GNB spacing and equiaxed cell size suggests a correlation between these microstructural features. The impact of solid solution atoms on the inter-wall spacing is established for chromium and hydrogen. Both decrease the GNB spacing because of a decrease of the cross-slip probability and stacking fault energy, combined to a shielding effect for the later. The effect of GNB spacing on strain hardening is discussed in terms of the length scale associated with GNBs and the effect of solute content.

Crystal plasticity modeling of the effect of precipitate states on the work hardening and plastic anisotropy in an Al–Mg–Si alloy

In this study the influence of precipitates on the mechanical properties and plastic anisotropy of an age hardenable aluminum alloy during uniaxial loading was investigated using crystal plasticity modeling. The kinetics model of Myhr et al. was used to obtain the solute and precipitate features after different cycles of aging treatment. The amounts of solute, precipitate size and volume fraction, and dislocation density varying during deformation, were used to calculate the slip system strength. An explicit term was obtained based on the elastic inclusion model for the directional dependency of internal stress developed by non-shearable rod shape precipitates. Also, a dislocation evolution model was modified to assess the anisotropic influence of non-shearable precipitate on work hardening, and the effects of solute content on the rate of dynamic recovery. It was found that the model results were in good agreement with experimental uniaxial flow stress obtained under different aging conditions. The application of the model to single crystal revealed that the precipitates can reduce crystallography anisotropy, which in part was attributed to the precipitate induced anisotropy.

Microstructure and tensile behavior of duplex low-density steel containing 5 mass% aluminum

The microstructure and tensile behavior of low-density steels containing 5mass% Al were investigated. An alloy obtained under a specific heat treatment condition showed deformation-induced martensitic transformation, which yielded excellent mechanical properties of a high tensile strength of >900MPa and a high total elongation of >50%. The volume fraction and grain size of the austenite depended on the annealing temperature, which resulted in a transition from stable to metastable behavior of the austenite. The effects of solute content on grains and of austenite grain size on stability were discussed.

Effects of solute content on grain refinement in an isothermal melt

It is well accepted in the literature that for effective grain refinement some solute is required in the melt to restrict the growth of the solid even if potent nucleating particles with a favourable physical nature are present. In this paper we investigate the effect of the solute on grain initiation in an isothermal melt, and an analytical model is developed to account for the effect of solute elements on grain size. This study revealed that the solute elements in the liquid ahead of the growing crystals reduce the growth velocity of the nucleated crystals and increase the maximum undercooling achievable before recalescence. This allows more particles to be active in nucleation and, consequently, increases the number density of active particles, giving rise to a finer grain size. The analytical model shows that the final grain size can be related to the maximum undercooling, average growth velocity and solid fraction at the moment of recalescence. Further analysis using the free growth model and experimental data in the literature revealed that for a given alloy system solidified under similar conditions the grain size can be empirically related to 1/ Q ( Q is the growth restriction factor) to a power of 1/3, which is considerably different from the empirical linear relationship in the literature. It is demonstrated that the 1/3 power law can describe the experimental data more accurately than a linear relationship.

On the variation of lattice parameter of Cu solid solution with solute content in Cu-Ti alloys

The properties and structure of age hardenable Cu-Ti alloys have been studied extensively to assess their suitability as a substitute for the toxic and expensive Cu-Be alloys. The earlier studies reported a sharp increase in hardness and strength and marked decrease in electrical resistivity in solution treated Cu-Ti alloys at Ti contents greater than 4.0 wt% and it was attributed to fine scale precipitation in the form of modulations in Cu-4.5Ti and Cu{sub 4}Ti, {beta}{sup 1} precipitate in Cu-5.4Ti alloys, formed during quenching itself. Further, such sharp changes were not observed in the peak aged condition due to uniform precipitation of Cu{sub 4}Ti, {beta}{sup 1} phase in all the four Cu-Ti alloys. However, the effect of solute content on the lattice parameter of {alpha}-Cu has not been investigated. The variation of lattice parameter of {alpha}-Cu with Ti content in solution treated (ST) and ST + peak aged conditions is presented in this paper.

炭素鋼のミクロ偏析におよぼす溶質濃度と凝固速度の影響

炭素鋼のミクロ偏析におよぼす溶質濃度と凝固速度の影響

The effect of solute content on grain boundary segregation in electron-irradiated Fe-Cr-Mn alloys

Solute distribution and microstructural development in the vicinity of grain boundaries in ferritic Fe-10 Cr- xMn-3 Al ( x = 5, 10 or 15) alloys were studied during electron irradiation to 10 dpa at 723 K. In addition, X-ray diffraction analysis was performed for determination of the volume size factor of solutes. The oversized solute atoms, manganese and aluminum, were depleted at grain boundaries, whereas the concentration of the oversized chromium rose sharply at the boundary. The amount of segregation of the solutes decreased with increasing atomic volume depending on manganese content. Segregation of aluminum, which had the greater volume size factor relative to that of manganese, was higher than that of manganese. The amount of radiation-induced segregation of manganese and aluminum at the grain boundary is consistent with arguments based on the atomic size effect, but the enrichment of chromium at the grain boundary is not and seems to related primarily to the formation of chromium-rich precipitates at the boundary.

Effect of solute content on the grain refinement of binary alloys

Data are presented for the grain refining of AI-Si and Pb-Sb alloy systems. These show a minimum grain size near the maximum solubility limit. An explanation in terms of the solidification interval is presented. In general, the optimum grain refining is predicted to occur at the solubility limit since t is at this concentration that the solidification times are longest.

Effect of heat treatments on the portevin-le chatelier effects in aluminium-silver alloys

The effect of solute content and heat treatment on occurrence of the P-L effect were investigated in AlAg alloys. The activation energies estimated from values of the critical strains were nearly equal to that for solute migration in AlMg alloys, which means that the P-L effects in AlAg alloys were caused by the same mechanism as in AlMg alloys. The P-L effects in Al-0.5 and 1.0 at.%Ag alloys occurred in the furnace cooled specimens only, on the other hand in 2.5 and 4.0% alloys it occurred in the quenched specimens only. In order to explain these results it seems better to adopt the cluster theory rather than the Cottrell theory.

The Effect of Solute Content on the Slip Behavior in 7XXX Series Aluminum Alloys

The microstructures of three high strength, high purity Al-Zn-Mg-Cu alloys, in the T6 temper, were characterized extensively using quantitative optical metallography and quantitative transmission electron microscopy. Only the solute content (Mg + Zn) of these alloys was varied for this study. These alloys were shown to be identical in grain size and shape, dispersoid (E-phase) and grain boundary precipitate (ν) populations, and precipitate free zone widths. The matrix microstructures consisted of ordered GP zones and ν′ and differed only in the volume fraction of these strengthening precipitates. The higher solute alloys had the higher yield strengths and volume fractions of matrix precipitates. Subsequent slip behavior analysis of prestrained tensile specimens demonstrated that slip band spacings and slip step heights increased with increasing solute content for the same macroscopic strain (ep = 0.02). A work softening model by Hornbogen and Gahr was shown to predict this tendency toward increased strain localization with higher solute levels.

Nickel and nitrogen ion irradiation induced void swelling and defect microstructures in Ni-Al, Ni-Cr and Ni-Ti solid solutions

The effects of solute content, temperature, and irradiation dose on the void swelling characteristics of pure nickel and several nickel base solid solutions (Ni-Al and Ni-Ti containing up to 8 at. pct solute and Ni-Cr containing up to 16 pct Cr) have been iNvesti-gated. Samples were irradiated in the temperature range 400 to 650°C to a maximum dose of 70 dpa using 3.5 MeV58Ni+, 400 keV14N+ and 400 keV14N+ 2 ions. The irradiation in-duced microstructures were studied using transmission electron microscopy. In general, the addition of Al, Cr or Ti to Ni is found to decrease the void swelling and mean void diameter and to increase the dislocation density. The behavior of the void number den-sity, Nv, as a function of solute content is found to be dependent upon the irradiation con-ditions as well as the particular solute addition. Nv passes through a maximum at approxi-mately 2 pct solute content for Ni-AI and Ni-Cr alloys irradiated at 550°C, but through a minimum at 4 pct for Ni-Ti alloys irradiated at 550 and 600°C. Nv decreases monotoni-cally as a function of Al content at 600 and 650°C. The results are discussed in terms of recent theories of void swelling suppression due to impurity or solute additions and in light of several correlations between void swelling and material parameters. The be-havior of Nv is found to be best described by the actions of two compcting processes. The first enhances void nucleation, is not strongly temperature dependent and is dominant at low solute contents. The second suppresses void swelling, is probably diffusion con-trolled and dominates in the more concentrated alloys.

Pitting potential of high purity binary aluminium alloys—I. AlCu alloys. Pitting and intergranular corrosion

The effect of solute content on the pitting potential of Al-Cu alloys in 1M NaCl solutions was studied. In solution treated Al-Cu alloys the pitting potential of the alloy was found to increase with increasing Cu content. The maximum pitting potential value was limited by the solubility of Cu in the Al. It was found that, while the pitting potential of pure aluminium was ca. −0.52 V, the pitting potential of Al-5.22% Cu was −0.33 V. The ageing of the alloy affected the pitting potential. The pitting potential of the aged alloy was found to be determined by the copper content of the solute depleted zones formed during ageing. The formation of G.P. zones did not modify the pitting potential of the alloy. The formation of θ′′ phase, in an Al-3.5 Cu alloy, produced a decrease of 30 mV in the pitting potential, while the formation of θ′ phase produced a decrease of > 100 mV. As ageing was more rapid in the grain boundaries, there was a localized decrease in the pitting potential, which was followed by susceptibility of the alloy to intergranular corrosion.

デンドライトの2次アームの間隔におよぼす溶質含有量の影響

デンドライトの2次アームの間隔におよぼす溶質含有量の影響